AC Immune’s Phase 2 Data Suggests Potential to Slow Parkinson’s Progression with ACI-7104.056
Promising Interim Results Show Biomarker Stabilization in Early Parkinson’s Disease
AC Immune (NASDAQ:ACIU) reported encouraging interim results from its Phase 2 VacSYn study evaluating ACI-7104.056, an active immunotherapy for early Parkinson’s disease (PD). For the first time, targeting the underlying alpha-synuclein (a-syn) pathology appears to potentially slow the progression of PD. These findings point toward disease stabilization in both clinical assessments and disease-related biomarkers, while maintaining a favorable safety profile.
ACI-7104.056 Elicits Robust Antibody Response and Achieves Key Targets
The trial enrolled 34 patients randomized 3:1 to ACI-7104.056 or placebo, with interim results reflecting at least 12 months of treatment for all and up to 18 months for some. Immunogenicity endpoints were robustly met, including:
| Endpoint | Outcome |
|---|---|
| Antibody Responder Rate | 100% |
| Serum Antibody Titer (Week 76) | Over 500x higher than placebo |
| CSF Antibody Titer | Over 500x higher than placebo |
| Serum/CSF Correlation (Week 24) | Spearman 0.92 (p<0.05) |
This immune response was consistently boosted with each immunization. Importantly, ACI-7104.056-generated antibodies crossed the blood-brain barrier, a critical milestone in developing therapies for neurodegenerative diseases.
Biomarker Stabilization Suggests Slowed Disease Progression
Several disease-relevant biomarkers in the central nervous system remained stable in the treatment group, a contrast to typical progression seen in the placebo arm:
- a-syn in CSF: Stabilized in the ACI-7104.056 arm; decreased in placebo (post-hoc p=0.018), suggesting targeted binding and possible brain clearance.
- Neurofilament Light chain (NfL): Stable in treated group; increased in placebo, indicating reduced ongoing neuronal damage.
- Other markers: Plasma glial fibrillary acidic protein (GFAP) and DaT SPECT imaging both showed trends towards stabilization of PD pathology.
Motor Symptom Trends Support Clinical Benefit
Motor symptom severity, measured by the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS Part III), showed promising trends. The ACI-7104.056 group did not show meaningful progression over 74 weeks, while the placebo group showed the expected decline. Results were even more pronounced when accounting for levodopa treatment state.
Safety Profile Remains Strong
ACI-7104.056 demonstrated a favorable safety profile with no serious adverse events reported related to the drug. The most frequent side effects were mild and included transient injection site reactions (56%), headaches (15%), and fatigue (12%). These safety results help strengthen the benefit/risk balance as development moves forward.
| Adverse Event | Incidence |
|---|---|
| Injection site reactions | 56% |
| Headaches | 15% |
| Fatigue | 12% |
| Serious events related to drug | 0% |
What’s Next for AC Immune and ACI-7104.056?
With these interim results in hand, AC Immune plans to seek regulatory guidance to potentially accelerate ACI-7104.056’s clinical path toward registration. The company expects final Phase 2 data in mid-2026. For investors and clinicians alike, the positive signal for disease modification in PD—along with an encouraging safety record—makes ACIU one to watch as the field advances toward precision medicine for neurodegenerative diseases.
Investor Takeaway
The consistency and magnitude of immunogenicity and biomarker stabilization shown in this interim analysis are encouraging signs. While it remains early days, ACI-7104.056 could represent a shift in Parkinson’s treatment if these results hold in further studies. With upcoming regulatory interactions and final trial data ahead, this is a pivotal moment for AC Immune and the wider PD treatment landscape.
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